Fuel metering device



NOV. l1, 1952 E. o. wlRTH ErAL FUEL METERING DEVICE Filed 001;. 17. 1947 NW MW Patented Nov. 11,71952 UNITED STATES TENT OFFICE FUEL METERING DEVICE Application (ctober 17, 1947, Serial No. 780,368

j Claims. l

The-present invention relates to fuel supply systems for internal combustion engines and more particularly to a mechanism for variably controlling the delivery of fuel by said system to meet engine requirements throughout the operating range.

One of the principal objects of the present invention is to provide a fuel system for internal combustion engines wherein a controlled supply of fuel for the engine is regulated in aC- cordance with certain engine variables including engine speed and throttle position.

Another object of the present invention is to provide a fuel system for the aforementioned engines in which the movement of the throttle valve increases the effective sise of the metering orifice in approximately straight-line relationship to increases in absolute manifold pressure and simultaneously therewith causes a temporary enrichment in the fuel-air mixture supplied the engine.

A further obieet of the invention is to provide a variable fuel metering orifice which can be readily adjusted without stopping the engine or Without removing any parts from the fuel metering device.

Further objects and advantages will be apparent from the following descrip-tion of the present invention illustrated by a specific detailed embodiment thereof. Although the drawing and the detailed description disclose but one specific embodiment of our fuel supply system, it is to be understood that many variations of structure and arrangement of parts are possible without departing from the scope of thev invention, and we contemplate the use of any such variations which may be desirable in meeting requirements.

In the drawing, numeral lil designates the body of an updraft carburetor, 2 a throttle valve, it an air inlet, and l5 a mixture outlet of the induction passage for an internal combustion engine or other fuel consuming device. A. controlled supply of liquid fuel is delivered to the induction passage by a metering unit consisting generally of a centrifugal pump 24J` adapted to receive fuel from a substantially constant pressure source through condui-t 22 and to discharge said fuelV at an increased variable pressure through conduit 24, a fuel metering orifice unit 25 and xed metering orifice 28, and thence to the discharge valve 3B and nozzle 32. An idle cut-off valve-generally shown at 3d may also be included in conduit 24 between metering orificev 28 and the discharge nozzle. The

(Cl. 12S-119) general arrangement of the fuel metering elements comprising the present fuel system is shown and described in detail in our copending application Serial No. 689,712, filed August 10, 1946, now Patent No. 2,443,527, issued June 15, 1948.

The centrifugal pump 28 consists of a fuel chamber 35 and an impeller 38 therein mounted on shaft @e which is iournaled in pump housing t2 and is adapted to be driven by the engine through a shaft or the like connected to the reduced portion rid of shaft lill. On the intake side of centrifugal pump Zi.) is a vapor bleed 45 which is preferably connected by a conduit to the fuel supply tank (not shown) to prevent vapor locking of the centrifugal pump.

The fuel discharged from centrifugal pump 20 is delivered through conduit 22S to fuel metering unit 25 mounted on carburetor body I!) adjacent throttle valve i2. rlhis unit is provided with a cylindrical valve element or sleeve it secured at one end to a flexible sealing diaphragm 48 and adapted to move axially in a cylindrical portion @Si of the metering unit housing Eil. Diaphragm :i3 is marginally clamped between housing 50 and support EL formed integrally with throttle body l@ and is reinforced by a metal stiffening member secured to the back side of said diaphragm by a rivet 58 extending therethrough into the base of cylindrical valve element 46. The metering orifice iin of said unit is disposed in the forward end of valve element it and the effective size thereof is varied, as said valve element reciprocates, by an adjustable tapered screw 62 threaded into the housing 5! in axial alignment with the metering orifice 50. Screw B2 is secured in its adjusted position by spring 553 reacting between the housing and the knurled head 64 of said screw. The cylindrical valve element 46 and metering orifice Si! are urged axially away 4from the tapered end of screw $2 by spring 66 reacting between the inner surface of housing Eil and the oase of said valve element. Fuel is admitted into the central passage of valve element l through a plurality of ports 58 formed in the side of said element near the base thereof. The back side of diaphragm assembly 4t abuts against an actuating cam 'ifi mounted on the end of the throttle shaft i3 and secured thereto by nut ill. During the operation of the engine, the valve element 4t is actuated in unison with the throttle valveby a throttle valve lever and linkage mounted on or connected to the free end of shaft i2.

The fuel delivered through metering'orifice 6U passes through one or more fixed metering orifices 3 28 disposed in the main fuel line 24 and thence through the orifice 80 of idle cut-off unit 34. The flow of fuel through orice 88 is controlled by a tapered valve 82 mounted in a reciprocable piston 84 which is actuated by a pinion 86 so disposed in said unit that it engages a rack formed in the surface of the piston 34. The pinion is rotated by a manually actuated lever 88 which may be operated from some remote place by a linkage secured to the end of said lever. During the operation of the engine, the tapered Valve 82 is completely withdrawn from orifice 80 and thus has no effect on the operation of the fuel supply system; however, when the engine is stopped, said tapered Valve is manually seated over orifice 82 to prevent the fuel from leaking into the engine induction system while the engine is not running.

The fuel passes from orifice 88 through main fuel conduit 24 to chamber 8|] of the discharge valve assembly and thence through conduit 92 to discharge nozzle 32. The discharge Valve 32 is regulated by a flexible diaphragm 94 marginally clamped between a boss on carburetor body |8 and housing SG of the discharge valve assembly. A second fuel chamber 88, which isseparated from chamber S8 by diaphragm 94, is connected by conduit |89 with the intake side of centrifugal pump 2|) and maintains at all times the same pressure as that of the fuel delivered to pump 28 from the source of supply, said latter pressure preferably being of a substantially constant value. The fuel, on leaving chamber 9D, flows into conduit S2 and passes into chamber |82 of nozzle 32 and there forms an emulsion with air supplied through conduit |4 from the air inlet |4 of the carburetor, the air being discharged into said chamber through a plurality of ports |83 disn posed in the side of the conduit. The annular groove |88 between the air and fuel conduits is the outlet port of the nozzle and is so calibrated that it forms a critical flow orifice which is adapted to prevent any substantial amount of engine suction from being transmitted from the intake manifold to chamber IEE. By this arrangement, engine suction is prevented from influencing the operation of valve 35, which would otherwise be affected if the fuel in conduit 32 were subjected to any substantial Variations in pressure. A venturi is disposed in the induction passage adjacent the critical flow nozzle for the purpose of obtaining an even distribution of the fuel in the air flowing through the induction passage and satisfactory air flow lines in said passage.

An accelerating pump generally shown at |29 is mounted on carburetor body IG adjacent the throttle valve |2 and is actuated by the throttle actuating mechanism through throttle shaft 'F2 and cam 'i8 mounted on the end thereof. A pump chamber |2| is formed by a pair of spaced diaphragms |22 and |24 separated from one another by a spacer element |26, the thickness of which determines the size of the pump chamber. In the central portion of diaphragm |24 and clamped thereto is a cylindrical element |32 which is adapted to reciprocate in a recess in the top portion of housing |34 of the pump and is urged downwardly, as shown on the drawing, by a spring |36 reacting between a stiffening member |38 on diaphragm |24 and an internal shoulder |46 of housing |34. A cylindrical element |42 is secured to the central portion of diaphragm |22 and is adapted to reciprocate in element |32. A coil spring |44 is mounted in cylindrical element |42 and reacts between the bottom thereof and the top portion of cylindrical element |32 and thereby urges the two diaphragms |22 and |24 apart and the base of cylindrical element |42 against cam 78. The pumping chamber |2| is connected to the main fuel conduit 24 by a conduit |50 which has a restriction |52 therein. Although only a single conduit is employed for both the fuel inlet and outlet of said pump, it may be desirable in some adaptations to use separate conduits having check valves disposed therein. In the operation of the engine when the throttle Valve is closed, spring |44 urges cylindrical element |42, together with diaphragm |22, downwardly against a depressed portion in the periphery of cam 70, thus enlarging chamber |2| and causing fuel to flow from conduit 24 through conduit |58 and restriction |52 into said chamber. During this time, diaphragm |24 is prevented from following diaphragm |22 by spacer element |26. The under side of the diaphragm is provided with a stiffening member |54 which engages and seats on the spacer element while the throttle valve is closed and diaphragm |22 is in its lowermost position. As the throttle valve is opened, fuel is discharged through conduit |58 and restriction |52 into main fuel conduit 24. However, should the throttle valve be opened at a rate greater than that at which the fuel can be fully discharged through restriction |52, diaphragm |24 is forced upwardly in opposition to spring |38, compressing said spring while maintaining chamber |2| at substantially the same capacity as that assumed when the throttle valve is closed. As the throttle Valve is held in open position, the pressure of spring |36 on diaphragm |211 grad ually forces the fuel from chamber |2| through conduit |55` and restriction |52, thus providing a gradual and sustained enrichment in the fuel-air mixture as the engine attains a desired speed. When the fuel has been discharged, the diaphragm |24 and stiffening member |54 again seat on spacer element |25. The pump is claimed in a divisional application Serial No. 258,151 filed November 14, 1951.

In the operation of the present fuel metering system, liquid fuel is supplied to the centrifugal pump 20 through inlet conduit 22 and is discharged by said pump through main fuel conduit 24 to fuel metering unit 26. The fuel then passes through variable metering orice 60 into conduit 24 through metering orifice 28, idle cutoff orice 80, conduit 24" and thence into chamber 98 of the fuel discharge valve. As the speed of the engine increases, the speed of the impeller likewise increases, causing the pressure of the fuel in conduit 24 to become greater and consequently causing the differential across metering orifices 60 and 28 to become greater. The pressure in conduit 24 anterior to the metering unit is at all times greater than the impeller inlet pressure by an amount directly proportional to the square of the impeller speed and therefore is proportional to the square of the engine speed. The pressure in conduit 24 and chamber 98 during operation is always less than the pressure in conduit 24 anterior to the metering unit by an amount equal to the inrease in pressure obtained by impeller 38. The difference in the two pressures constitutes the total effective metering head across metering orifices 28 and 80. Since the quantity of fuel which will flow through a given size metering orifice will vary in proportion to the square root of the differential between the pressures of the unmetered fuel and the metered fuel on opposite sides of the metering orifice, and since this difference varles with the square of engine speed, the quantity of fuel iiowing through orifices 28 and 60 for a given setting of valve element 46 will vary directly as the engine speed.

An increased ow of fuel produces a temporary rise in the pressure of chamber 90 and thus forces diaphragm 94 and valve portion 30 thereof away from the inlet end of fuel conduit 92, thereby permitting a greater flow of fuel into the discharge nozzle.

As the throttle valve is opened, cam l0 permits the cylindrical valve element 46 to move away from tapered screw 62, thus increasing the effective size of orice 60, screw 62 preferably being so contoured that the effective size of orice 69 varies in approximately straight-line relationship with absolute manifold pressure as the throttle valve is opened or closed. Also, as the throttle valve is opened, cam 'l0 urges diaphragm |22 toward diaphragm |24, thus forcing additional fuel into conduit 24 and causing a further, though temporary, rise in pressure in chamber 90 and consequently a greater flow of fuel through the discharge nozzle. This produces a temporary enrichment in the fuel-air mixture delivered to the engine. Rapid or successive operation of the present accelerating pump does not produce excessive enrichment of the fuel-air mixture since the pump is not in effect positively actuated, but

rather is yieldably urged by spring 136 to discharge fuel when the throttle valve is opened. It is seen that by the present construction a sustained increased flow of fuel is obtained by the enlargement of the effective size of the metering orifice when the throttle valve is opened, together with a temporary further increase for enrichment of the fuel-air mixture While the engine is attaining the desired speed.

We claim:

1. In a fuel supply system for an engine having an induction passage with a throttle valve therein: a main fuel conduit; a pressure creating means in said conduit; a metering restriction in said conduit; a means, actuated as the throttle valve is moved toward open position, for increasing the effective size of said metering restriction in approximately straight-line relationship with increases in absolute manifold pressure; and a mechanism operable simultaneously with said second mentioned means for temporarily further increasing the flow of fuel in said conduit.

2. In a fuel supply system for an engine having an induction passage with a throttle valve therein: a main fuel conduit; a means in said conduit for varying the fuel pressure therein in response to variations in engine speed; a metering restriction in said conduit; a means actuated by the throttle actuating mechanism for increasing the effective size of said metering restriction in approximately straight-line relationship with increases in absolute manifold pressure; and a device operable simultaneously with said second mentioned means for temporarily further increasing the flow of fuel in said conduit.

3. In a fuel supply system for an engine having an induction passage with a throttle therein: a fuel supply conduit; a means for varying the pressure of the fuel in said conduit in accordance with engine speed; a metering restriction in said conduit posterior to said pressure varying means; a valve element actuated by the throttle actuating means for controlling the effective size of said restriction; a discharge Valve downstream from said restriction; and a device also actuated by the throttle actuating means for temporarily increasing the ow of fuel in said conduit when the throttle is moved toward open position.

4. In a fuel supply system for an engine having an induction passage with a throttle therein: a fuel conduit; a means for varying the pressure of the fuel in said conduit by an amount substantially proportional to the square of engine speed; a metering restriction in said conduit posterior to said pressure varying means provided with a throttle actuated valve for increasing the effective size of said metering restriction in approximately straight-line relationship with increases in absolute manifold pressure; a discharge valve downstream from said restriction; a means including a passageway communicating with said conduit anterior to said pressure varying means for controlling said discharge Valve; and a device actuated by the throttle actuating means for temporarily increasing the flow of fuel through said conduit when the throttle is moved toward open position.

5. In a fuel supply system for an engine having an induction passage with a throttle therein: a fuel supply conduit; a means for varying the pressure of the fuel in said conduit in accordance with engine speed; a restriction in said conduit posterior to said pressure varying means; a valve member actuated with the throttle for varying the effective size of said restriction; and a mechanism operable simultaneously with said member for temporarily increasing the ow of fuel in said conduit.

EMIL O. WIRTH. FREDERIK BARFOD.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,010,247 Frederick Nov. 28, 1911 1,970,626 Rockwell Aug. 21, 1934 2,103,629 Moore Dec. 28, 1937 2,123,485 Moore July l2, 1938 2,440,241 Armstrong Apr. 27, 1948 2,502,679 Stanly I Apr. 4, 1950 

